Hemostatic changes in Rocky Mountain spotted fever and Mediterranean spotted fever

Rocky Mountain spotted fever and Mediterranean spotted fever are rickettsia l infections primarily of endothelial cells that normally have a potent ant icoagulant function. As a result of endothelial cell infection and injury, the hemostatic system is perturbed and shows changes that vary widely from a minor reduction in the platelet count (frequently) to severe coagulopathi es, such as deep venous thrombosis and disseminated intravascular coagulati on (rarely). Changes favoring a hypercoagulable state include endothelial i njury and release of procoagulant components, activation of the coagulation cascade with thrombin generation platelet activation, increased antifibrin olytic factors, consumption of natural anticoagulants, and possibly high le vels of coagulation-promoting cytokines. Yet, most studies have been perfor med on endothelial cell cultures that provide nonphysiologic, reductionisti c, experimental conditions. The lack of flow, platelets, and WBCs makes the se experiments far from simulating the response of endothelial cells in the human body. Coagulopathies and thrombotic events should be considered as p otential complications of severe Rocky Mountain spotted fever and Mediterra nean spotted fever.